1. Field of the Invention
This invention relates to a method of and apparatus for detecting the presence of live organisms in substances. A particular application of the invention is to the detection of the presence of bacteria or viruses in very small numbers in substances.
2. Description of the Prior Art
It is known that all or most live cells each contain a large number of ATP (andenosine-5'-triphosphate) molecules, many or all of which molecules are released if the cell is disrupted, that is to say, the outer cell membrane ruptured and the cell contents dispersed. (ATP molecules in dead cells are quickly broken down by autolysis.) It is also known that when ATP molecules react with firefly essence (i.e. "Luciferin" reagent and "Luciferase" enzyme) photons of light are produced according to the following formula: EQU Luciferin+ATP+O.sub.2 (Luciferase/Magnesium ions) light photons
That is to say, the andenosine-5'-triphosphate ("ATP") molecules react with the reagent Luciferin in the presence of oxygen and magnesium ions and the Luciferase enzyme to produce light photons, one photon per ATP molecule. A living cell may contain approximately 100 ATP molecules. Reference may be made to an article entitled "The energy source for bioluminescence in an isolated system" by W. D. McElroy in Volume 33 (1974) page 342-345 of the Proceedings of the National Academy of Science and to another article entitled "Luminometry - a sensitive technique in analytical chemistry and medical sciences" by S. Kolehmainen at pages 129-135 of the September/October 1979 issue of "International Laboratory".
Even a single light photon can be detected by a suitably positioned photo-multiplier (PM) to produce an electric pulse output. However the PM has to be highly sensitive for this purpose, rendering the PM liable to produce electric pulse outputs in response to spurious disturbances as "noise". Furthermore, impurity ATP molecules react with the firefly essence to produce photons of light.
It is also known that a bacterium cell (and possibly even a virus) can be ruptured (or burst open) by violent agitation alone (e.g. ultrasonically) or with a cutting agent (if not ultrasonically) such as aluminium oxide, ballotini beads, sand or carborundum, in water.